# SecKeyGenerateSymmetric(_:_:) Generates a random symmetric key. ``` func SecKeyGenerateSymmetric(_ parameters: CFDictionary, _ error: UnsafeMutablePointer?>?) -> SecKey? ``` ## Parameters `parameters` A key generation parameter dictionary. At minimum, this must contain [`kSecAttrKeyType`](/documentation/Security/kSecAttrKeyType) and [`kSecAttrKeySizeInBits`](/documentation/Security/kSecAttrKeySizeInBits). In addition, this function assumes default values for the following keys: - [`kSecAttrLabel`](/documentation/Security/kSecAttrLabel) defaults to `NULL`. - [`kSecAttrIsPermanent`](/documentation/Security/kSecAttrIsPermanent) if this key is present and has a value of , the key or key pair will be added to the default keychain. - [`kSecAttrApplicationTag`](/documentation/Security/kSecAttrApplicationTag) defaults to `NULL`. - [`kSecAttrEffectiveKeySize`](/documentation/Security/kSecAttrEffectiveKeySize) defaults to `NULL`, which means the effective key size is the same as the key size ([`kSecAttrKeySizeInBits`](/documentation/Security/kSecAttrKeySizeInBits)). - [`kSecAttrCanEncrypt`](/documentation/Security/kSecAttrCanEncrypt) defaults to for private keys, for public keys. - [`kSecAttrCanDecrypt`](/documentation/Security/kSecAttrCanDecrypt) defaults to for private keys, for public keys. - [`kSecAttrCanDerive`](/documentation/Security/kSecAttrCanDerive) defaults to . - [`kSecAttrCanSign`](/documentation/Security/kSecAttrCanSign) defaults to for private keys, for public keys. - [`kSecAttrCanVerify`](/documentation/Security/kSecAttrCanVerify) defaults to for private keys, for public keys. - [`kSecAttrCanWrap`](/documentation/Security/kSecAttrCanWrap) defaults to for private keys, for public keys. - [`kSecAttrCanUnwrap`](/documentation/Security/kSecAttrCanUnwrap) defaults to for private keys, for public keys. These default values can be overridden by adding a value for the associated key in the parameter dictionary. When used as a replacement for [`SecKeyGenerate`](/documentation/Security/SecKeyGenerate) , set the [`kSecUseKeychain`](/documentation/Security/kSecUseKeychain) key to the keychain ([`SecKeychain`](/documentation/Security/SecKeychain) ) into which the key should be stored, [`kSecAttrLabel`](/documentation/Security/kSecAttrLabel) to a user-visible label for the key, and [`kSecAttrApplicationLabel`](/documentation/Security/kSecAttrApplicationLabel) to an identifier defined by your application, for subsequent use in calls to [`SecItemCopyMatching(_:_:)`](/documentation/Security/SecItemCopyMatching(_:_:)) . Additionally, you can specify keychain access controls for the key by setting [`kSecAttrAccess`](/documentation/Security/kSecAttrAccess) to a [`SecAccess`](/documentation/Security/SecAccess) object. `error` A pointer to a variable where an error object is stored upon failure. If not `NULL`, the caller is responsible for checking this variable and releasing the resulting object if it exists. ## Return Value A newly generated symmetric key, or `NULL` on failure. In Objective-C, call the function to free the key’s memory when you are done with it. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)